Many different kinds of earplugs of the above-mentioned type have been known for a long time. For a long time, use has been made of a core or body part having the character of a stem, at the front part of which a substantially softer sealing part was attached in some suitable manner.
Recently, earplugs of the type mentioned by way of introduction have been manufactured, completely made of elastic polymeric material of a suitable hardness, the sealing part as a rule comprising transversely protruding flange or collar portions, which extend circumferentially and are adapted to engage sealingly with the wall of the auditory canal. In this context, it has been indicated that the core or body part could be made of a material having a higher hardness than the material of the sealing part, but owing to manufacturing difficulties, use has been made of a single polymeric material for the entire plug. This has necessarily resulted in a compromise between axial rigidity (which should be high in order to facilitate insertion) and radial rigidity (which should be low for good adaptation to the auditory canal with maintained comfort).